Process for purifying sulphur



Aug. 15, 1939. c. 0, LEE Er AL PROCESS FOR PURIFYING summm Original Filed March 24, 19156 2 Sheets-Sheet l INVENTORS 0 X420 J W am ATTOR EYs c. 0. LEE ET AL 2,169,261

PROCESS FOR PURIFYING SULPHUR 4, 1936 2 Sheets-Sheet 2 Aug. 15, 1939.

Original Filed March 2 \NVENTORS ORNEYS Patented Aug. 15, 1939 UNITED STATES PATENT OFFICE PROCESS FOR PURIFYING SULPHUR Delaware Application March 24, 1936, Serial No. 70,572 Renewed March 9, 1938 8 Claims.

This invention relates to a process of purifying sulphur, and has for its object generally to provide an improved procedure for purifying sulphur, whereby the process may be practiced in an eflicient and economical manner.

More specifically, the invention relates to a process of purifying sulphur obtained from mining by underground fusion whereby hydrocarbons and other impurities that discolor and otherwise reduce the value of the mined sulphur are removed.

Another object is to practice the purification of a crude sulphur product by distillation without interference from the high viscosity ordinarily attendant in the heating of a body of molten sulphur to the temperature of vaporization.

Another object is to provide a resultant sulphur product substantially devoid of hydrogen sulphide and other adsorbed gaseous impurities.

A further object is to provide an improved procedure for removing carbon and other solid products resulting from the breakdown of hydrocarbons during the distillation of sulphur whereby there is recovered additional sulphur to augment the product obtained by distillation.

Other objects of the invention will in part be obvious and will in part appear hereinafter.

The invention accordingly comprises the several steps and the relation of one or more of such steps with respect to each of the others thereof, which will be exemplified in the process hereinafter disclosed and the scope of the invention will be indicated in the claims.

For a fuller understanding of the nature and objects of the invention reference should be had to the following detailed description taken in connection with the accompanying drawings, in which:

Fig. 1 is a view partly in section and partly in elevation showing an arrangement of apparatus adapted for the practice of the invention; Fig. 2 is a similar view of a modified form of apparatus adapted for the practice of the invention;

Fig. 3 is a fragmentary view partly in section and partly in elevation showing an arrangement of apparatus for practicing an auxiliary purifying step in conjunction with the apparatus shown in Figs. 1 and 2; and

Fig. 4 is a fragmentary view showing a detail of the lower boiler drum employed in Fig. 2.

In the mining of sulphur from underground deposits by the method of underground fusion, the sulphur deposits are frequently near petroleum and other sources of hydrocarbons. The

sulphur mined by underground fusion as a result contains impurities which operate to discolor the product, impair its burning characteristics, and otherwise detrimentally affect the value of the product. 5

Several methods of treating the sulphur mined by underground fusion with various reagents toremove the undesired impurity have been pro posed. Such treatments, however, have invariably proved either insufliciently eifective to re- 10 move the impurity to the desired extent or are too costly for commercial purposes. Mechanical removal of impurities of this character is, in general, impractical because of the intimate distribution of the impurities and the high viscosity 15 of the molten sulphur.

By the present process, the product obtained by underground fusion is purified by distillation; the heating being performed in a manner which avoids the difliculties due to viscosity. The breakdown of the hydrocarbons, which takes place on account of heating, gives products which are separated and purified, yielding a final purified product of high commercial quality that has the characteristic brilliant yellow color of pure sulphur.

In the ordinary method of sulphur distillation, it is not possible to make a separation of the hydrocarbon impurities in the liquid sulphur, and the resulting product is a sulphur containing some volatile hydrocarbon oils and finely divided carbonaceous impurities caused by the reaction of the volatile oils and the sulphur in the vapor state. This produces a sulphur with a color varying from green to black. For this reason, it has been necessary to use a sulphur of less than .03% of hydrocarbon impurities when making flowers of sulphur by distillation in the usual retort. In the present invention, a process has been developed for distilling sulphur at high rates by means of tubular equipment which yields a brilliant yellow color and is substantially free from impurities, regardless of the amount of such impurities initially present.

The first step of the process involves relatively rapidly heating the sulphur containing the un- 45 desired impurity, in a liquid state, through the viscous temperature range by contacting the sulphur with sulphur Vapors in a direct contact heater. This initial heating step is accomplished in any suitable manner, for example, by spraying the sulphur into an atmosphere of sulphur vapors, or by introducing the sulphur into pans which will distribute the sulphur uniformly in a container filled with sulphur vapors. It is preferable to effect this heating in a countercurrent fashion; that is, introducing the sulphur vapors into the bottom. of the container and allowing them to flow upward to the outlet and introducing the molten sulphur at the top of the container and allowing it to flow by gravity to the bottom of the container. In this fashion, the sulphur vapors could be condensed by the incoming liquid sulphur and no sulphur vapors will escape from the top of the heating element. In this heating step, a reaction occurs between the hydrocarbon impurities and the sulphur forming hydrogen sulphide gas and a non-volatile impurity containing carbon.

The second step of the process involves holding the heated sulphur at or near the boiling point for a period sufficiently long to efiect a substantially complete reaction between the volatile hydrocarbons and the sulphur; a period of approximately 30 minutes is sufficient for commercial purposes. This step results in producing heat treated sulphur containing no volatile impurities other than a trace of hydrogen sulphide gas.

The third step of the process involves a relatively slow application of heat to the heat treated sulphur in a still to yield sulphur vapor together with the volatile impurities present, which vapors are withdrawn into a tubular condenser where the latent heat of vaporization is extracted and the liquid cooled to a temperature of approximately 300 F. At such temperature the sulphur is relatively easily handled or conveyed by pumps or other suitable means to a vat for cooling and storage.

The fourth step of the process involves purification. of the distillate and the removal of the volatile impurities therefrom. This is preferably accomplished in conjunction with the condensation of the sulphur vapor since here the volatile impurities may be released and separated by virtue of the decreased solubility of hydrogen sulphide in liquid sulphur as the pressure decreases. Additional removal of hydrogen sulphide from I the liquid condensate consists of adding ammonia gas which reduces the solubility of the hydrogen sulphide in the liquid sulphur and permits subsequent removal by blowing with a purging agent, such as air. This causes the volatile impurities to be expelled by virtue of the decreased solubility thereof which results from increased temperature. The latter is preferably practiced as an additional or auxiliary step of purification.

The removal of non-volatile impurities from the concentrate or bottoms which collects in the distilling apparatus may also be practiced as an additional purification step, but such step is not essential to the process of the present invention. When practiced, these bottoms are withdrawn for treatment either intermittently or continuously and represent a relatively small proportion of the total sulphur being treated, the quantity depending, of course, upon the amount of impurity in the sulphur originally to be removed. These Withdrawn bottoms may be cooled by means of a suitable cooling medium and the carbon separated. The purified sulphur resulting may be added to the main portion of the purified sulphur product. The product produced in the condenser and that separated from the concentrated bottoms, upon removal of the carbon and associated impurities, results in a product which is a relatively high percentage of that originally introduced for treatment. The process is adapted for either small or large production and may be carried on either as a batch process or continuously. The amount of sulphur remaining in the bottoms, which contain the non-volatile impurities, is frequently too small to justify treatment for recovery and can easily be disposed of.

In Fig. 1 an arrangement of the apparatus for the continuous practice of the process is shown. Here a conduit 10 is provided to supply molten sulphur containing the undesired impurity. The rapid heating through the viscous temperature range is practiced by means of a preheating vessel l I, arranged to supply heat to the molten sulphur by causing the latter when introduced to condense sulphur vapor. To this end, the vessel H has a distributing vessel or spraying head l2 disposed at the top from which the molten sulphur is sprayed or otherwise distributed in an atmosphere of sulphur vapor that is supplied through conduit l3. The heated sulphur collects in the bottom of vessel l l, which contains sufficient storage space for the hot molten sulphur to be held in retention for a sufiicient period or time to complete the reaction between the hydrocarbon impurities and the heated sulphur, and is withdrawn through conduit M to be supplied through conduit l5 to the still I6 that is located in a heating chamber or furnace IT. A pump 14 is preferably inserted at the junction of conduits l4 and [5, so that the flow of sulphur through these conduits may be made to take place at a desired toms are passed over through a conduit I8 into a separating chamber [9. The vapor products are withdrawn through the conduit 2| and in troduced into the condensing chamber of a tube condenser 22 that has headers 23 and 23' for distributing a cooling medium, such as water,

through the tubes to efiect the desired condensation of sulphur vapor. As the sulphur vapor is condensed, any non-condensible impurities, such as hydrogen sulphide, may readily escape through a vent tube 24 which is provided for the condenser. The condensed purified sulphur product which collects in the bottom of condenser 22 is withdrawn through a conduit 25 to a bin or other suitable place where the sulphur is collected and cooled into a solidified body of commercially pure sulphur. The passage of the sulphur, as liquid or vapor, is, of course, controlled in the various conduits by means of valves introduced at suitable points; for example, conduit has a control valve l0; conduit IS, a valve [5; conduit 2|, a valve 2|; and conduit 25, a valve In the event that the sulphur product withdrawn through the conduit 25 is not sufiiciently purified and still contains hydrogen sulphide, an additional step of purifying may be practiced. Accordingly, an auxiliary purifying device is connected so that the product may be by-passed into the same for treatment. To this end, valve 25' is closed to stop the direct flow of sulphur and cause the same to pass into the auxiliary purifying vessel 25, this vessel having an inlet connection 2'! controlled by valve 21 leading from the conduit 25 at a point between the valve 25' and the condenser 22 and a similar connection 28 leading from the bottom into a secondary purifying vessel 29, which has a connection 30 leading from the bottom controlled by a valve 30 and connecting with the conduit 25 at a point beyond the valve 25, The auxiliary purifying vessel 26 is preferably provided with a steam jacket 3| for maintaining the sulphur in a molten state. A vent connection 32 is provided at the top of the auxiliary vessel 26 for withdrawing the released hydrogen sulphide. The vessel 26 is also provided with a filling material 33, such as ceramic rings for filming the sulphur in its downward flow through the vessel and providing surface of contact for ammonia vapors which are introduced through a connection it near the bottom of the vessel. This causes a release of the hydrogen sulphide which is allowed to escape through the connection 32. The sulphur, when being additionally purified, is passed from vessel 26 through the conduit 28 into the secondary treating vessel 25 which may likewise contain a filling similar to that in the vessel 26, over which the sulphur flows downwardly and then out of the bottom of the vessel 29 through the conduit 30 to a point where it joins with the conduit 25. Air is introduced into the vessel 29 through a connection 35 connected near the bottom, the air passing out through a vent connection 36 at the top of the vessel. This sweeps out any remaining ammonia or hydrogen sulphide from the purified sulphur.

Certain volatile constituents initially in the liquid sulphur supplied for purification may be removed in the vessel H, since this vessel applies the first heat treatment. Accordingly, a connection 3? is led from the top of the vessel H to the atmosphere for disposing of the volatile impurities which consist mainly of hydrogen sulphide gas and unreacted hydrocarbon vapors. The connection l3, which introduces vapor to the vessel H, is arranged to be supplied with vapor directly from the separator NJ. The conduit l3 may be supplied with sulphur vapor from any suitable source, but it is preferably connected to the separator l9 as the source, and is so shown. Conduit l3 accordingly has a valve l3 for controlling the supply of vapor from the vessel l9 to the vessel H. The separator l9 may have any convenient form, and is shown as an elongated vessel having a space for collecting the vapors to be withdrawn which is provided with bafiles 38 disposed and arranged to deflect fine condensed particles of sulphur so that they are returned to the body of the liquid in the separator 59. The portion of the sulphur or bottoms which contains the concentrated impurities in the separator I9 is in the form of a sludge or pasty fluid and is withdrawn through a conduit ll preferably connected to lead from the lowermost portion of the separator. This sludge may be discharged either to an external point for storage as a low grade product, or to a suitable carbon removing device.

It is desirable on occasion to accelerate the passage of the sulphur through the still in order to utilize properly higher rates of heat transmission and quicken the treating process. To this end, the still and separator are preferably provided with a recirculating connection 4| which leads from the bottom of the separator l9 and has interposed therein a control valve 4! and a suction pump 42. This connection is arranged to feed back into the supply line H].

The steps of the process to be practiced in purifying sulphur are carried out with the apparatus above described as follows: Sulphur in a molten state from an original source of supply and containing an undesired hydrocarbon impurity is conveyed by the conduit IE! to the preheater II, the liquid sulphur being introduced therein through the distributor l2 as a spray through an atmosphere consisting of the vapors of sulphur. This spray is thus rapidly heated by condensing the sulphur vapors into liquid sulphur at a temperature substantially above the viscous range; the viscosity normally having a maximum value occurring between 350 and 500 F. The sulphur thus heated in the preheater is conveyed through the conduits M and I5 into the still I6 and the desired heat applied in the furnace I! by means of burning fuel to cause vaporization of a major portion of the liquid; both vapor and liquid being then conveyed to the separator I9. In the ractice of these steps of heating, the valves Ill and I5 are normally open, while valve 4| is closed. The initial volatile impurities in the sulphur, heated in the preheater H, pass out through the conduit 31.

The sulphur vapor produced in the separator I9 is normally continuously withdrawn through the conduit 2|, the valve 2| being normally open, the valve I3 being also open sufficiently to supply enough vapor through the conduit l3 to produce the desired preheating efiect. The sulphur vapor produced in the separator is, withdrawn through the conduit 2|, together with any hydrogen sulphide impurity, are conveyed to the condenser 22 where thei sulphur vapor is condensed to liquid sulphur, the hydrogen sulphide normally escaping through the connection 24. The condensed sulphur is then withdrawn through the conduit 25 and discharged into a vat where it may be cooled and stored. The valve 25' is normally open during the period of withdrawals while valves 21 and 30' are closed.

When it is desired to practice the additional purifying step for the removal of the hydrogen sulphide the valve 25 is closed and valves 21 and 30 are opened so that sulphur is passed into the auxiliary vessel 26 where it is maintained molten by means of a steam jacket 3| and ammonia introduced through the conduit 34 and air introduced into the second auxiliary vessel 29 through a conduit 35. The resulting product is, of course, sulphur of a very high degree of purity.

The steps of rapid heating, holding for reaction, distillation and separation practiced by the separate organs shown in the apparatus depicted in Fig. 1 may be practiced more expeditiously in a specially constructed apparatus when desired. An arrangement of this character is shown in Fig. 2, Here, the sulphur heating apparatus is in the form of a water tube boiler which comprises an upper holding and preheating drum 5!! and a. separating drum 5! that communicates with the former through liquid and vapor connections 52 and 53, respectively, together with a lower drum 54 that has connections to the drum 5! through a plurality of inclined risers 55 and 56. The boiler is disposed so as to be heated in a furnace and has a bailie between risers 55 and 56 so that circulation is thermally induced up riser 55 and down riser 56.

In this arrangement, the conduit l conveys the liquid sulphur from the source intothe preheating drum 50, the sulphur input being preferably discharged by means of a spraying head l2. The sulphur vapor, which distills off in drum collects in dome 5! and is led off through to the condenser 22 which has a sulphur condensate. withdrawal conduit 25, arranged in any suitable manner, for example, in the same manner as shown in Fig. l.

The practice of the process with the second form of apparatus is substantially the same as with the apparatus of Fig. 1. The liquid sulphur to be purified is introduced into the heating apparatus through the conduit Ii the rapid heating through the viscous stage being efiected by condensing the sulphur vapor suppliefd thereto through the connection preheating drum 5B, and conduit 52. In this apparatus, the sludge or bottoms fluid is withdrawn from the lower drum 54 by a conduit '55 and is conveyed either to a carbon removing device or to a storage vat for solidification. By proper actuation of the valves associated with the conduit the sludge may be withdrawn either continuously or intermittently.

I'he sulphur vapor distilled ed in the separating drum 5! is conveyed by the conduit iii to the condensing chamber of a condenser 22 and is cooled by any suitable medium, for example, water, and the condensate withdrawn through a conduit 25 leading from the bottom of the condensing chamber which may have the same form as shown in Fig. 1. Here, the main step of separating the volatile impurities, such as hydrogen sulphide, is accomplished and led away through a conduit 24. Conduit conveys the purified product to a storage vat. Means, however, may be associatetl with this conduit for practicing of an additional step of purification, which additional step may be the same as that shown and described in connection with Fig. 1, or an equivalent one, such as the alternative one described more fully hereinafter.

Where the drums in a boiler of the character shown in Fig. 2 have considerable length, it is not feasible to collect the sludge for withdrawal by the use of a single conduit 16 unless provision be made for the collection of this sludge at a desired point in the drum, for example, at one end, to which the conduit ii} is connected. An

arrangement of this character is shown in Fig. 4, where the lower drum is provded with suitable collecting means in the form of a screw conveyor 56, which has a shaft 6i passing through a stuffing boX 62 formed on the end of a collecting dome 63 secured to one end of the drum. The outer end of the shaft El is arranged to be driven by suitable driving means, for example, an electric motor 64, which may be geared thereto, as indicated. In this arrangement, the sludge withdrawing conduit 65 leads from the lower portion of the collecting dome 63 and conveys the sludge to the desired point.

Suitable apparatus for practicing additional purification of the sulphur condensate in a way alternative to that above described is shown in Fig. 3. Here, the sulphur condensate is discharged from the condenser through a conduit 25 and collected in a settling tank '58. This settling tank may comprise a relatively large receptacle in the form of an open tank or vat that is constructed of concrete and provided with a heating coil "H disposed about the bottom. In this vat, the additional or supplementary purification is accomplished by the mechanical admixture of a suitable releasing agent, for example, iron oxide taken in the proportion of about 1% by weight of the molten sulphur. Accordingly, the vat i8 is shown as provided with mechanical agitating means ll disposed therein and driven by an electric motor. The hydrogen sulphide escapes to the atmosphere, the iron oxide having been added as desired from any suitable source, and is thereafter me nanically removed. To this end, a withdrawal conduit 12 leads from a suitable point in the vat to a filter "(3. Suitable forcing means, such as a pump 14, is advantageously introduced in conduit 12 in order that a flow through the conduit and the filter may be made to take place at a desired rate. The liquid sulphur which passes through the filter is conveyed into a second settling tank 15 that is similar to tank but is pref erably disposed below it and preferably also has a heating coil, as shown at 16. Both tanks 10 and are advantageously provided with drains which are shown respectivelyatll and T8, the drain from the tank 10 being preferably arranged to drain into the tank T5. The tank 15 is also provided with a withdrawal conduit 19 leading from a suitable point and has introduced therein a motor-driven centrifugal pump 80. Further purification is mechanically accomplished in the tank 1'5 and the product lead away through conduit 19 to a storage vat.

It will be seen that the apparatus here provided for the present invention accomplishes substantially the complete removal of hydrogen sulphide from the sulphur product here produced, the process of removal being accomplished through the practice of four main steps, the last of which is the purification step per so which may be accomplished in a number of different ways provided the sulphur has been properly conditioned by the preparatory steps here set forth,

Claims for the apparatus, however, have been divided out of this case and transferred to the copending application, Serial No. 166,942, filed October 2, 1937, in the name of Lee and Smith, and which is a continuation-in-part of the present application.

Since certain changes in carrying out the above process and in the constructions set forth, which embody the invention, may be made without departing from its scope, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

Having described our invention, what we claim as new and desire to secure by Letters Patent is:

1. A process for purifying crude sulphur that contains a hydrocarbon impurity, which comprises relatively rapidly heating the crude sulphur in the liquid state by contact with sulphur vapor to a temperature relatively near the boiling point to react the sulphur with said impurity, thereafter continuing the heating substantially to complete the reaction of the sulphur with said impurity and produce a distillate consisting of sulphur vapor and a volatile product together with a sludge or bottom, and then separating the sulphur vapor from the volatile impurity whereby a highly purified sulphur product is obtained.

2. A process for purifying crude sulphur th.\t contains a hydrocarbon impurity, which comprises relatively rapidly heating the crude sulphur in the liquid state by contact with sulphur vapor to a temperature relatively near the boiling point to react the sulphur with said impurity, thereafter continuing the heating substantially to con1- plete the reaction of the sulphur with said impurity and produce a distillate consisting of sulphur vapor and a volatile product together with a. sludge or bottom, withdrawing said distillate, and then condensing the sulphur out from the distillate.

3. A process for purifying crude sulphur that contains a hydrocarbon impurity, which comprises relatively rapidly heating the crude sulphur in the liquid state by contact with sulphur vapor to a temperature relatively near the boiling point to react the sulphur with said impurity, thereafter continuing the heating substantially to complete the reaction of the sulphur with said impurity and produce a distillate consisting of sulphur vapor and a volatile product together with a sludge or bottom, withdrawing said distillate, then separating the sulphur from the distillate, and during distillation removing sludge from the further heated sulphur.

4. A process for purifying crude sulphur that contains a hydrocarbon impurity, which comprises relatively rapidly heating the crude sulphur in the liquid state by contact with sulphur vapor to a temperature relatively near the boiling point to react the sulphur with said impurity, thereafter continuing the heating substantially to complete the reaction of the sulphur with said impurity and produce a distillate consisting of sulphur vapor and a volatile product together with a sludge or bottom, withdrawing said distillate, separating hydrogen sulphide from the distillate by cooling the same to condense sulphur and decrease the concentration of hydrogen sulphide in the sulphur, and then additional- 1y purifying the sulphur condensate.

5. A process for purifying crude sulphur that contains a hydrocarbon impurity, which comprises relatively rapidly heating the crude sulphur in the liquid state by contact with sulphur vapor to a temperature relatively near the boiling point to react the sulphur with said impurity, thereafter continuing the heating substantially to complete the reaction of the sulphur with said impurity and produce a distillate consisting of sulphur vapor and a volatile product together With a sludge or bottom, Withdrawing said distillate, separating hydrogen sulphide from the distillate by cooling the same to condense sulphur and decrease the concentration of hydrogen sulphide in the sulphur, and then additionally purifying the sulphur condensate by flushing with a gas that assists in effecting the release of volatile impurities.

6. A process for purifying crude sulphur that contains a hydrocarbon impurity, which comprises relatively rapidly heating the crude sul phur in the liquid state by contact with sulphur vapor to a temperature relatively near the boiling point to react the sulphur with said impurity, thereafter continuing the heating substantially to complete the reaction of the sulphur with said impurity and produce a distillate consisting of sulphur vapor and a volatile product together With a sludge or bottom, withdrawing said distillate, separating hydrogen sulphide from the distillate by cooling the same to condense sulphur and decrease the concentration of hydrogen sulphide in the sulphur, further treating the condensate by admixing a metallic oxide, absorbing hydrogen sulphide, and filtering the resulting mixture to obtain a relatively highly purifled sulphur product.

'7. In a process for purifying crude sulphur that contains a hydro-carbon impurity, the steps which comprise heating the crude sulphur in the liquid state rapidly through the viscous temperature range by contacting the liquid sulphur with sulphur vapor, and then further heating the liquid sulphur to an elevated temperature in the neighborhood of the boiling point and holding the same at said elevated temperature for a period of time such that a carbon residue results from the reaction of sulphur with the hydrocarbon impurity.

8. In a process for purifying crude sulphur that contains a hydrocarbon impurity, the steps which comprise feeding crude molten sulphur into a chamber, finely dividing the sulphur fed so that it may pass as a current of sulphur particles, thereafter generating a vapor phase from the molten sulphur so fed by the application of heat to the same, introducing said vapor phase into said chamber, and causing the vapor phase so introduced to move in contact with said sulphur particles and in a direction countercurrent to the passage of the molten sulphur.

CLARENCE 0. LEE. HOMER A. SMITH. 

